鄂尔多斯盆地东南部上古生界地层压力与天然气分布

 鄂尔多斯盆地东南部上古生界近几年勘探成果备受瞩目,但针对本地区地层压力及与天然气分布关系的研究较少。本文通过293 口井实测的压力数据和154 口井的测井数据分析发现,二叠系上石盒子组-太原组泥岩普遍存在“欠压实”特征,4 个目标层位在压力剖面上分异明显,可划分为石炭系本溪组常压系统和二叠系山2 段-盒8 段负压系统。现今地层压力分布总体上具有东北高西南低的特点,二叠系压力分布与沉积相分布具有较好的一致性。“欠压实”泥岩层控制气藏纵向上的分布。二叠系气藏主要分布在负压地层中的“低压”部位,而石炭系本溪组气藏则主要分布在常压地层中的“高压”区域。发现地层压力与气藏分布关系对于本地区天然气勘探其有重要指导意义。

Formation pressure and distribution of natural gas in the Upper Paleozoic,southeastern Ordos Basin

Exploration achievements in the Southeastern Ordos Basin have attracted tremendous attention in recent years. However, few researches about distribution of formation pressure and relation with natural gas have been carried out in this area. The measured formation pressure data of 293 wells and well log data of 154 wells are analyzed in this paper, and the results show that the mudstones from Upper Shihezi Formation to Taiyuan Formation of Permian are mostly undercompacted, and that the variations with depth of formation pressure in 4 target layers have obvious differentiation, which can be divided into negative pressure system of Permian and normal pressure system of Carboniferous in further. The distribution of current formation pressure is high in the east and north and low in the west and south, the relation between sedimentary facies and distribution of formation pressure in Permian are in a good consistency. Gas reservoirs on vertical zonation are controlled by the under compacted mudstone layers, and also can be found in the "low pressure" areas of negative pressure stratum in Permian and "high pressure" regions of normal pressure in Carboniferous. The discovery of the relation between formation pressure and gas reservoirs is significant for the following natural gas exploration in this area.